1. Field of the Invention
This invention relates generally to windshield wiper assemblies, and more particularly to a winter boot for protecting a windshield wiper assembly from harsh environmental conditions.
2. Description of Related Art
A critical problem encountered by windshield wiper designers has been how to maintain contact between a wiper blade and a windshield at all times throughout the windshield wiping process. One complicating factor is that a particular wiper blade may be designed to fit on many different automobile models. Different automobiles typically have windshields of different sizes and shapes, and providing contact between the windshield and all parts of a wiper blade can be a difficult task. One design solution to the problem has been to provide wiper frames having spring-like flexural members attached to the frames. The flexural members exert forces at various points along the wiper blade to insure contact of the blade with the windshield.
A bare windshield wiper is rendered largely ineffective during winter weather when snow, sleet, or ice accumulate on the flexural members of wiper frames. The movement of the flexural members is hindered which prevents the frame from applying the correct forces to the wiper blade. Since the wiper blade does not fully contact the windshield, the wiping effectiveness of the wiper blade is significantly decreased.
The windshield wiper boot, sometimes called a “winter boot,” has been used to protect windshield wiper frames that are subjected to harsh winter weather conditions such as snow, sleet, and ice. The primary purpose of the winter boot is to prevent ice and snow from accumulating on the flexural members and other joints of a windshield wiper frame. Typical winter boots are made of natural rubber or ethylene propylene diene monomer (EPDM) because the materials provide good tear resistance and are easy to manufacture. The natural rubber and EPDM used in wiper blades, however, perform poorly when subjected to low temperatures such as those encountered in freezing climates. For example, when natural rubber is subjected to temperatures around 0° C. (32° F.), the material reaches a glass transition temperature and begins to lose flexibility. Since the winter boot surrounds the wiper frame, the decreased flexibility of the winter boot hinders the proper movement of the flexural members and joints of the wiper frame. The overall result is poor contact between the wiper blade and the windshield, which reduces the wiping ability of the wiper blade. Additionally, EPDM and natural rubber deteriorate rapidly when exposed to ultra-violet radiation and ozone.
A need exists, therefore, for a winter boot made from a material having good tear resistence and superior resistance to ultra-violet radiation, ozone, and extreme temperatures, especially low temperatures. A need also exists for a wiper assembly having a wiper frame that is covered by a winter boot having the above-mentioned properties. Finally, a need exists for a winter boot that is easily manufactured.